A principal objective of the research outlined in this proposal is to explore the early events involved in the action of growth hormone on target cells which lead to the stimulation of protein anabolism. The hypothesis that the direct effects of growth hormone on protein synthesis and related metabolic events are mediated in the rat diaphragm by a lowering of the cellular level of cyclic AMP is being studied. Also the relationship of somatomedin to the direct action of growth hormone on muscle metabolism is being explored. Finally studies are being initiated to determine the nature of the growth hormone molecule that circulates and is the biologically active moiety.